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Re: Stormbergia dangershoeki, new Early Jurassic ornithischian from South Africa
T. Michael Keesey
> ... and ceratopsians and pachycephalosaurs as derived ornithopods. At
> least, that's how I read Butler's tree.
Depends on which definition of _Ornithopoda_ you are following. Sereno
(1997) considered it a node-based clade, and anchored it on
_Heterodontosaurus_ and _Parasaurolophus_ (1998), but in the latest edition
of The Dinosauria, it is "all cerapodans closer to _Edmontosaurus_ than to
_Triceratops_", which explicitly excludes _Marginocephalia_.
Using Butler's tree, these two definitions give an Ornithopoda that are very
different in content.
"Classic" Ornithopoda is a massively paraphyletic assemblage roughly
equivalent to "unarmored
_Ornithischia_" or "bipedal _Ornithischia_". In adapting it to cladistic
taxonomy, there seems to be a consistent desire to restrict it to a
particular lineage (a la _Amphibia_) rather than expand it to include
descendants (a la _Dinosauria_), probably because the very popular term
"Ornithischia" is already available for the expanded group (not to mention
Yes, the traditional/classical Ornithopoda also included scelidosaurs,
psittacosaurs and pachycephalosaurs. So I can't see why Ornithopoda
shouldn't be node-based and expanded to include pachies and ceratopsians,
should the topology show that iguanodontians and marginocephalians are
closer than previously thought.